Tonight, it's all coming to an end. After five and a half seasons of TV's craziest roller coaster ride, Pretty Little Liars fans are finally going to find out who A is. Throughout all of PLL's past five seasons, showrunner I. Marlene King has been the most secretive about A's identity. That's because, up until recently, she was the only person who knew it. Now that the official reveal is set for tonight, she's speaking out about why she chose A's true identity, and why some fans won't be happy with tonight's big reveal.

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"Everyone has their own favorites of who they want to be 'A' and no matter who it is, there will be certain group of people upon that initial face who will say, 'Oh I didn't want it to be that person,'" Marlene revealed to ET Online. "But I think the story is so compelling that for the rest of the episode, getting to hear the story, and see the story play out of how 'A' became 'A', you realize that there could be no other 'A'. It had to be this person."

While Marlene won't ruin the surprise for fans, she did confirm one fact about A. When asked about why Ali has been more sympathetic to A lately, she replied, "Well, 'A' is her brother."